1. Field
The present disclosure relates generally to protection for fasteners. In particular, the present disclosure relates to a method and apparatus for sealing fasteners.
2. Background
In composite structures, the sealing of metal surfaces and the holes that penetrate the structure may have a number of purposes, including the reduction of fuel leakage, with respect to fuel leaking out of the tank, the reduction of other fluids entering or exiting the fuel tank, the coverage of metal components that can have a propensity to accumulate electrical charge, or the prevention of galvanic corrosion.
Components, such as metallic fasteners, may be sealed. Sealant in the form of seal caps may cover these fasteners. A “seal cap” is a structure that covers an end of a metallic component. The metallic component may be a fastener. The end may be the head fastener or the threaded end of the fastener with a nut. The fastener may be, for example, a bolt, a screw, or some other type of fastener.
For example, a seal cap may be attached to the end of a fastener that extends into the interior of the fuel tank. This seal cap is configured to provide a seal against the flow of fuel out of the fuel tank. The seal cap may also reduce or eliminate the accumulation of electrical charge on the surface of the exposed fastener.
Seal caps are often comprised of materials that retain sealing properties when submerged in fuel and/or when left dry for different periods of time. For example, molded polymeric seal caps may be used in fuel tanks for aircraft. These types of seal caps may fit over the protruding end of a fastener on the interior of the fuel tank. Sealants may be placed into the seal caps prior to the seal caps being placed on the fastener. The sealant may be in the form of a plastic forming material.
For example, a seal cap may have an interior that is partially filled with an uncured sealant. This seal cap with the sealant is then pressed into place on the fastener. When in this position, excess sealant extrudes from around the bottom of the cap. This sealant may be blended around and onto the exterior of the cap. The sealant is then allowed to cure to form the final sealant material.
However, installing molded seal caps may take an undesirable amount of time. For example, molded seal caps may be placed over fasteners manually. Manual installation may take an undesirable amount of time. Further, molded seal caps may be manually inspected for voids prior to installation over fasteners. Yet further, blending extruded sealant may be performed manually and require training to meet desired tolerances.
Therefore, it would be desirable to have a method and apparatus that take into account at least some of the issues discussed above, as well as possibly other issues.